.- Metalworking fluids (MWF) are complex mixtures widely used in motor vehicle manufacturing, aerospace and a variety of other industries as lubricants and coolants. Human exposure is increasing internationally despite the presence of known carcinogens, such as chlorinated compounds and polycyclic aromatic hydrocarbons in oil-based fluids, and ethanolamines and nitrosamines in water-based fluids. In response to a recommendation by the National Institute of Occupational Safety and Health for reduced exposure limits in 1998, the Occupational Safety and Health Administration added MWF to its list of priority substances for consideration, but formal guidelines were never issued. In 2004, the National Toxicology Program (NIEHS) announced plans for long-term animal testing of MWF to help address lingering uncertainty regarding the carcinogenic risk posed by ongoing exposures. [unreadable] [unreadable] [unreadable]